This is a case-control study of the epidemiology of prolapsed lumbar intervertebral disc and prolapsed cervical intervertebral disc. Demographic characteristics and exposure to possible risk factors in surgical, probable, and possible cases of each of these conditions in the age range 20-64 years will be compared to demographic characteristics and exposure to possible risk factors in two control groups in the same age range. All cases and controls are people who have sought medical care at hospitals and at physicians' offices. One control group is composed of people without known spinal disorders and the second comprises people with back and neck problems other than prolapsed discs. Persons with previous prolapsed discs or other previous significant back or neck problems are excluded from the case and control groups. Information on demographic variables and exposure to possible risk factors is obtained by means of a structured questionnaire administered by trained interviewers. The possible risk factors of particular interest are driving motor vehicles and using other modes of transportation, occupational characteristics such as prolonged sitting and frequent twisting motions, pregnancies, participation in certain sports, respiratory symptoms, height, and weight. Data collection for this study is now taking place.